marine animals

Pas de contenu pour le moment

Humpback whales are long-range migrators, on the recovery after heavy whaling during more than 150 years. Understanding where they feed in the polar oceans, and why they might choose an area rather than another is helped by Argos telemetry tracking.

Populations recovering from whaling, but not the same everywhere

Since the early 19th century humpback whale (Megaptera novaeangliae) populations were hunted to near extinction; overhunting of whales was already a concern at the time when J. Verne wrote 20,000 leagues under the sea’ in 1869. Following a moratorium on whaling in 1966, the populations are recovering, but they are still threatened by various human activities such as entanglement in fishing gear, collisions with ships, and noise pollution. The Oceania humpback whales, comprising whales from multiple sub-populations spanning from New Caledonia to French Polynesia, are estimated to be less than half of their pre-exploitation numbers and recovering slower than the neighboring east Australian population.

Long-range migrators

Humpback whales feed on krill in the polar waters during summer, and breed in the tropical oceans during winter, relying on their stored energy reserves to support breeding and the long-distance migration. The cues that the whales use to navigate between their feeding and breeding grounds are still not fully understood. With such far-ranging migrations in remote waters, especially in the polar areas, the only feasible way of better understanding their travels is to use satellite telemetry transmitters, such as Argos.

But knowing where they have been is just the beginning. Using probabilistic movement models on Argos-transmitted locations can help to identify different behaviors – when they are “looking around” in search of food (Area Restricted Search, which can also be indicative of resting or breeding), or going from one foraging area to another (transiting). These behaviors can then be related to environmental variables such as sea surface height, surface currents, sea ice concentration and distance to the ice edge, keeping in mind an important lag effect in the ice edge dynamics.

Migration pathways for 18 Oceania humpback whales satellite-tagged at the Kermadec Islands, New Zealand. Left, the whale tracks with color-coding showing their behavioral state (red: inferred foraging, black: inferred transit, grey: uncertain), with a zoom on feeding ground overlaid on bathymetry (bottom). Right, the same tracks, colors representing the month of the locations. (Credit University of Auckland)
Migration pathways for 18 Oceania humpback whales satellite-tagged at the Kermadec Islands, New Zealand. Left, the whale tracks with color-coding showing their behavioral state (red: inferred foraging, black: inferred transit, grey: uncertain), with a zoom on feeding ground overlaid on bathymetry (bottom). Right, the same tracks, colors representing the month of the locations. (Credit University of Auckland)

 

Two foraging areas

Two major foraging areas were thus identified for Oceania humpback whales, one within the Amundsen and Bellingshausen Seas (right on the figure), and another north of the Ross Sea (left on the figure). The two areas likely have different prey dynamics and distribution, which vary within the summer feeding season. In the Amundsen and Bellingshausen Seas, the whales were foraging mostly near the continental shelf break and near the ice edge, where high densities of krill are expected to be found. North of the Ross Sea the whales were located in a reported biodiversity hotspot. This suggests that the humpback whales utilize different environmental cues, with some cues being of greater importance for whales in one area than the other, and that behavioral plasticity is important for these animals. This could be to their advantage since the environmental conditions in the Southern Ocean are fast changing. Data on the Oceania whales across multiple years could help identify persistent patterns in the whales’ behavior to determine the role of memory and assess the stability of the two feeding areas over time.

 

Photo :  Humpback whale with tag (Credit University of Auckland)

References

  • Leena Riekkola, Virginia Andrews-Goff, Ari Friedlaender, Rochelle Constantine, Alexandre N. Zerbini, Environmental drivers of humpback whale foraging behavior in the remote Southern Ocean, Journal of Experimental Marine Biology and Ecology 517 (2019) 1–12, https://doi.org/10.1016/j.jembe.2019.05.008
Humpback whale and tag (Credit University of Auckland)

31.07.2019 Animal tracking applications Argos helps in tracking where humpback whales feed

Humpback whales are long-range migrators, on the recovery after heavy whaling during more than 150 years. Understanding where they feed in the polar oceans, and why they might choose an area rather than another is helped by Argos telemetry tracking. Populations recovering from whaling, but not the same everywhere…
The young arctic fox female with an Argos collar (Credits Elise Strømseng, Norwegian Polar Institute)

19.07.2019 Animal tracking applications From Svalbard to Canada, the long travel of an arctic fox tracked by Argos

Arctic foxes are living in all the regions around the Arctic ocean. Argos satellite telemetry tracking demonstrates that some of those foxes are changing continent using the sea ice as bridge, travelling thousands of kilometers in a few months in the process, from Svalbard to Canada. ‘Recordfox’ of distance Since…
A whooping crane with an Argos PTT on its right leg (Credit Louisiana Department of Wildlife and Fisheries)

17.07.2019 Animal tracking applications Argos helps track large scale movements of Whooping Cranes reintroduced into Southwestern Louisiana

Whooping cranes were nearly extinct in North Americas in the 1950s. Preservation actions initiated since then have enabled the protection of the species. Reintroduction programs, helped by Argos satellite telemetry are now increasing the populations, and enabling new discoveries on those emblematic birds. Whooping Cranes (Grus americana) are large birds…
Group of Mhorr gazelle with a GPS collar (credits T. Abáigar)

03.07.2019 Animal tracking applications Reintroducing Mhorr gazelles into the wild

The Mhorr gazelle is an endangered species of the Sahelian area. It is one of the most singular, threatened and scarcely-studied gazelle species of northern Africa. It is considered by locals as part of their cultural wealth. Reintroduction into the wild of captivity-bred individuals has first been tried in Southern…
IMOS glider

01.07.2019 Flash news Glider recovery with Argos back-up tracking

Australia’s Integrated Marine Observing System (IMOS) is a national collaborative research infrastructure, supported by the Australian Government. The IMOS Ocean Gliders facility operates a fleet of autonomous underwater ocean gliders that undertake measurements from shelf and boundary currents in Australian waters. They recently recovered…

26.06.2019 Flash news Great news for Argos users, the Kinéis constellation carrying the future of Argos is under production!

Production is underway on the new constellation of 25 nanosatellites called Kinéis, with the next generation Argos instruments onboard. The new generation of the Argos system is based on greater bandwidth, improved data timeliness thanks to a shorter revisit time (5-15 minutes between satellite passes depending on latitude) and two-way…

14.06.2019 Animal tracking applications Happy World Sea Turtle Day from Argos

On June 16th, people around the world celebrate the beauty of sea turtles and their importance to the marine ecosystem. CLS, unique operator of the Argos system since 1986, would like to take this occasion to honor the scientists working to understand and protect sea turtles globally.  The Argos system…
loggerhead turtle

14.06.2019 Animal tracking applications Understanding the tracking of three loggerhead turtles with ocean data

Trajectories of loggerhead turtles in the Atlantic ocean and the Mediterranean Sea have been tracked using Argos transmitters. Comparing the tracks with marine environmental data provides a better understanding of the movements of these animals. Photo courtesy of Aquarium La Rochelle SAS. 35 years of monitoring…. For more than 35…
fiordland crested penguin

11.06.2019 Animal tracking applications New Zealand’s Marathon Penguins

New Zealand is home to more penguin species than any other country in the world. The Tawaki penguin, also known as the Fiorland penguin (Eudyptes pachyrhynchus), is one such species that breeds on the New Zealand mainland. With an estimated population size of merely 5,500–7,000 mature birds, Tawaki are very…
An elephant seal track (CEBC/CNRS), with the elephant turning around the low eddy on the right (sea level anomaly map dating from that turn)

29.05.2019 Animal tracking applications Ocean data to better understand marine animals in their environment

Argos satellite tracking makes it possible to follow the paths of tagged animals. This tracking data is invaluable, but sometimes it raises more questions than it answers. Why is the animal making a detour – or even a loop? Does it stay here or there for feeding, or for another…